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Physics at ALICE for the ALICE collaboration Paul Kuijer, NIKHEF

Physics at ALICE for the ALICE collaboration Paul Kuijer, NIKHEF. Detector status and performance Physics analyses pp Plans for PbPb. Detector overview. Optimized for PbPb collisions: High granularity (dN/dy~8000) Minimized material. Data Acquisition (DAQ) Detector Control System (DCS)

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Physics at ALICE for the ALICE collaboration Paul Kuijer, NIKHEF

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  1. Physics at ALICEfor the ALICE collaborationPaul Kuijer, NIKHEF • Detector status and performance • Physics analyses pp • Plans for PbPb

  2. Detector overview • Optimized for PbPb collisions: • High granularity (dN/dy~8000) • Minimized material Data Acquisition (DAQ) Detector Control System (DCS) High level trigger (HLT)

  3. Detector configuration 2010 ITS, TPC, TOF, HMPID, MUON, V0, T0, FMD, PMD, ZDC (100%) TRD (7/18) EMCAL (4/12) PHOS (3/5) HLT (60%) full hadron and muon capabilities partial electron and photon

  4. ALICE Performance TPC acceptance = 90% Momentum resolution ~ 5% @ 100 GeV Low material budget low pt cut off

  5. Charged Particle Acceptance SPD • operating with fast multiplicity trigger L0 from Silicon Pixels FMD V0

  6. Trigger configuration 2010 • based on interaction trigger reading all detectors: • SPD (min bias) or V0-A or V0-C • at least one charged particle in 8 pseudorapidity units • and single-muon trigger reading MUON, SPD, V0, FMD, ZDC : • single muon, low-pT threshold, in the muon arm in coincidence with interaction trigger • activated in coincidence with the BPTX beam pickups: • ‘bunch-crossing’ with bunches from both sides • for control ‘bunch-crossing’ with bunch from side A or C only • for control ‘bunch-crossing’ with no bunches • a fraction of ‘bunch-crossing’ trigger (no condition on trigger detectors) • for control • to measure relative fractions of single- and double-diffractive events • High multiplicity trigger from SPD • Studying up to which multiplicity to go • HLT in Mode B (no event rejection)

  7. Data taking since March 30th since February till end of March cosmic-ray data taking • ~105 events pp run since March 30th 2010 • 7 TeV • >600x106 events • 0.9 TeV • 7x106 events all triggers interaction triggers muon triggers (x50) 0.9 TeV TPC now running at 900 Hz

  8. Offline data processing 5TB Volume Raw data registration 16.3 1.4 LHC restart 30.3 • Run processing – start immediately after RAW data transferred to CERN MSS • Average – 5 hours per job • At 10 hours, 95% of the runs are processed • At 15 hours, 99% of the runs are processed Frequency 5h 10h 15h Raw data processing • Pass 1-6 completed for 0.9 and 2.36 TeV data • Pass 0 @T0 introduced for calibration • Pass 1 @T0 for 7 TeV data follows the data taking • Analysis train running weekly: QA, physics working groups organized analysis MC production Several production cycles for 0.9, 2.36 and 7 TeV pp with various generators (Phytia, PHOJET) and conditions from real data taking HI productions starting

  9. HLT, DAQ, DCS HLT – infrastructure and front-end nodes completed for PbPb computing nodes needs to upgrade HLT vertex reconstruction (used for LHC feedback) HLT K0S reconstruction DAQ, DCS, ECS – new Automatic Configuration Tool Create and archive a set of known good configurations Select from this set according to beam condition and physics program Software wizard to configure all the detectors and online systems

  10. Inner Tracking System – SPD Alignment precision Vertex reconstruction precision ALICE performance April 2010 s=16 mm/√2 Fully installed – still problem with cooling (insufficient flow of cooling fluid) improvements: freon sub-cooling close to detector; flow-meters and pressure regulators on each line typically ≥ 80% of half-staves operational fraction of dead pixels (in active half-staves) ~1.2%

  11. Inner Tracking System – SDD, SSD M. Chojnacki, E. Biolcati ALICE performance April 2010 ALICE performance April 2010 SDD – 94% (3) and 91.5% (4) operational improved calibration of drift velocity residuals ~ 60 mm (nominal 35 mm) SSD – 138 half-ladders operational (96%) alignment within ~ 20 mm calibration of dE/dx for PID ITS alignment: JINST 5 P03003 (2010) s ~ 20 mm

  12. Time-Projection Chamber p (GeV/c) Detector fully operational: 99.9% of all channels dE/dx resolution: < 5% momentum resolution: < 7% at 10 GeV working on distortion map: dp/p < 5% at 10 GeV read-out rate up to 1kHz J. Alme et al., ALICE TPC coll., Nucl. Instr. Meth. A (in print), arXiv:1001.1950 No vertex cut !

  13. Transition-radiation detector 7 out of 18 supermodules installed production on schedule – will be adjusted according the length of winter shutdown installed supermodules aligned with tracks gain calibration with g→e+e- K0s→p+p-

  14. Time-of-flight detector Fully installed – 95% channels operational Time resolution – close to nominal b σTOF=σ/√2 = 88 ps

  15. PHOS, EMCal, HMPID, PMD Hits Distribution Preshower plane CPV plane p K p PHOS – 3 out 5 modules installed and working at operational temperature – 25 C calibration in progress EMcal – 4 out 12 modules installed calibration in progress 6 modules prepared for installation HMPID – fully installed alignment and calibration in progress PMD – 90% of channels operational

  16. Muon detector Fully installed – muon chambers 95% of channels operational stable operation, alignment not finalized yet Trigger – 99% channels operational stable operation, at L0 trigger on pt > 0.5 GeV trigger – track matching matching efficiency

  17. Amount of material measured with gamma conversions

  18. Physics analyses • 5 papers published – accepted • Charged-particledensity in 900 GeV pp collisions • K. Aamodt et al. (ALICE), Eur. Phys. J C 65 (2010) 111 • Charged-particlemultiplicity in 0.9 and 2.36 pp collisions • arXiv:1004.3034[hep-ph] accepted in Eur. Phys. J C • Charged-particle multiplicity in 7 TeV pp collision – letter • arXiv:1004.3514[hep-ph] accepted in Eur. Phys. J C • Measurement of antiproton/proton ratio in pp at 0.9 and 7 TeV • Phys.Rev.LettVol 105, No 7 (2010) • Charged-particle transverse momentum spectra at 0.9 TeV • http://arxiv.org/abs/1007.0719, Phys. Lett. B • 1 paper submitted • Identical particle correlation in pp at 0.9 TeV • http://arxiv.org/abs/1007.0516, Phys. Rev. D • 2 papers in draft • Identified charged hadron spectra and yields in pp at 0.9 TeV • Strange particle production in pp at 0.9 TeV • Other analyses well underway • High multiplicity pp events, azimuthal correlations, event structure, p0 spectra, charm production,...

  19. dNch/dh versus √s Relative increase in dNch/dh ALICE CMS dNch/dh versus√s Inelastic Nch ≥ 1 in |h|<1 NonSingleDiffractive all Inelastic Good news for the Heavy Ion program: More charged particles corresponds to a denser and hotter system ! fits ~ s0.1 Results: - dNch/dh well described by power law (√s)0.2 • increase with energy significantly stronger in data than MC’s • Alice & CMS agree to within 1 s (< 3%) 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  20. Multiplicity distribution ALICE CMS Multiplicity distribution 7 TeV Multiplicity distribution 900 GeV Results: • most of the ‘stronger increase’ is in the tail of Nch • ALICE & CMS still agree perfectly ! 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  21. Momentum distribution 900 GeV pT distribution Comparison to MC’s <pT>versus√s Results: • Finally some (slight) difference ! • Spectrum seems to get harder towards midrapidity • MC’s have hard time to describe the full spectrum

  22. <pT> versus multiplicity pT for different multiplicities <pT> vs Nch Results: • Change concentrated at pt > 1 GeV (pQCD) • (surprisingly little change below ) • MC’s have hard time… 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  23. MC scoreboard • MC << data • MC >> data • MC ≈ data 0.9 TeV Stay tuned ! 2.36 TeV 7 TeV Conclusion: • none of the tested MC’s (adjusted at lower energy) does really well • tuning one or two results is easy, getting everything right will require more effort • (and may, with some luck, actually teach us something on soft QCD rather than only turning knobs) 23 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  24. Bose–Einstein correlations (HBT) BE enhancement vs qINV BE enhancement vs qINV pp Pb+Au unlike sign p+p- high Nch, kT high multiplicity high momentum radius ~ 1/width (Phojet) baseline low multiplicity low momentum kT • QM enhancement of identical Bosons at small momentum difference • enhancement of e.g. like-sign pions at low momentum difference qinv=|p1-p2|, as function of multiplicity and pair momentum kT = |pT1+pT2|/2 • measure Space-Time evolution of the ‘dense matter’ system in heavy ions coll. • interpretation in ‘small systems’ (pp, e+e-) is less obvious.. • ‘enhancement’ rel. to phase-space and any non-BE correlations (‘baseline’) • non-BE correlations important at high √(s) (‘minijets’)

  25. HBT @ 900 GeV Source Radius vs pair momentum Using different Baselines Radius vs kT Source Radius vs Multiplicity • Results: • Radius increases with Nch, comparable to ISR, RHIC, TeV • rather constant vs <kT> ! • sign. systematic uncertainty from ‘baseline’ shape • dependence usually interpreted as sign of ‘flow’ in heavy ions • neglecting non-BE correlations (‘flat baseline’) can cause kT dependence (at high √ s)!

  26. Baryon transport in pp Baryon transport via the di-quark Fragmentation function of di-quark exponentially suppressed at large rapitity gap • Baryon transport via di-quark, quark-J or Junction alone • Different fragmentation functions • G.C. Rossi and G. Veneziano, Nucl Phys. B123(1997)507 • exponentially suppressed, intercept model dependent • . Kopeliovich, Sov. J. Nucl. Phys. 45, 1078(1987) • Probability constant with rapidity d u u String Junction Traditional u d u u d J Large rapidity gap (9.6) at LHC  Difference in tails can be measured u

  27. Baryon – antibaryon asymmetry in pp Ratio  most instrumental effects cancel Hijing-B, Perugia-SOFT, QGSM(ε=0.024, αJ = 0.9) incompattible with the data

  28. Pbar/p ratio Little room for additional stopping

  29. Identified particles (preliminary) Kaon pT distributions stable & decays Identified Particle pT p K p 6 ways to measure Kaons … K → m n K0S → pp p ITS dE/dx K p TPC dE/dx TOF 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  30. Charged: p, K, p at 900 GeV 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  31. Decays: K0S, L, X, f at 900 GeV * X + X → L p L → p p K0S → pp • Preliminary results: • MC well below Data • more so at high pT • more so for L & X • f ~ ok (at least some MC) f → K K * 2009 Data (~300 k events)

  32. L/K0Sratio 900 GeV |h| < 1 L/K0S Ratio in Au+Au at RHIC |y| < 0.75 large Baryon/Meson ratio: parton coalescence from QGP ? • very good agreement between STAR (200 GeV) and ALICE (900 GeV) • very different from CDF (630/1800) and UA1 (630) for pT > 1.5 GeV • - UA1(630) and CDF(630) don’t agree either … • to be further investigated (different triggers, acceptance, feed-down correction ?)

  33. …and much more to come... K*→ K p X → L p W → L K < 2% of statistics at 7 TeV S*→ L p

  34. p0 and h from  conversion Raw π0 dN/dpT • e± identification in TPC (TRD soon) • study of  conversion points/material budget • EMCAL and PHOS, calibration in progress 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  35. Charm at 7 TeV D0→ K p p p Impact Parameter Resolution vs pT D+→ K p p D*→ D0 p 80 mm @ 1 GeV D0→ K p

  36. Charm at very low pT 2 GeV D0 cross section vs pT in |y| < 1 FONLL pQCD calculation • most of the cross section at low pT • shape at low pT very uncertain • 109 MB events => measure below 1 GeV • (PID important at low pT !) 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  37. J/y @ 7 TeV J/y → e+e- |y| < 1 J/y → m+m-, y = 2.5–4.1 • tough to measure J/y with our current low luminosity (also 1st year Pb–Pb luminosity will be very low -> priority on MB in pp) • ‘proof of performance’ higher luminosity later this year and next year 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  38. J/y → m+m- The acceptance and efficiency corrected distributions are compared to generated MC distribution Javier Castillo ICHEP2010 – Paris, France – 22/10/2010 38 • “CDF pp 7TeV” parameterization • pT extrapolated from CDF results • y obtained from CEM calculations • No polarization ( = 0)

  39. J/y → m+m- <pT2> vs √ s <pT> vs √ s 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  40. Event shape analysis S┴ vs Multiplicity 900 GeV S┴ vs Multiplicity 7 TeV Transverse sphericity S┴: eigenvalues of the momentum tensor Sxy small S┴: large S┴:

  41. pQCD: High-pT particle correlations Associated pTt Δf Trigger ‘near’ side ‘away’ side UE Trigger Particle Trigger Particle: highest pT particle in event (pTt) Associate Particle: all the others (pTa) 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  42. ‘High’-pT particle correlations pTt pTt • correlations present down to very low pT • study ‘mini-jet region (difficult with fully reconstructed jet ?) 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  43. Charged ‘mini-jets’ Width of ‘near’ side correlation => jT average transverse momentum of fragments relative to jet axis independent of √ s (well known) Width of ‘away’ side => <pT>pair ~ mean jet acoplanarity ( ~ kT) increases with √ s 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  44. UE vs. MC 06/08/2010, ALICE @ ICHEP Paris 2010, Karel Safarik, CERN Overview of LHC physics

  45. Planned quick PbPb analysis Wait until November for PbPb High multiplicity pp event multiplicity v2 pT (RAA, RCP) HBT high pT correlations

  46. Conclusions • 2010 running very successful • all detector, online, and offline systems ready • Alignment and calibration under control • about 500 million events collected • Physics analysis well underway • Heavy ions are our core business, starting in November • Meanwhile study QCD with pp collisions • Anti-baryon/baryon, HBT R vskt, Lambda/K, ...

  47. Just startedon pp, more to come Eagerfor PbPb

  48. Backup

  49. The LHC (and everything else) accelerates .. .. and tense anticipation.. ..after concentrated preparations.. Monday, 23rd November, ~15:30 in the ALICE Control Room

  50. some anxious minutes waiting for collisions.. ~ 16:35

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